Enable execution in a particular context directory.

[nathanhammond]

We use this library inside of Ember CLI's testing story, but we need a way to be able to execute in a particular directory. The current pattern for doing that looks like this:

process.chdir(...);
quickTemp.makeOrRemake(...);
process.chdir(...)

That's far less than ideal. This PR enables this invocation pattern:
quickTemp.makeOrRemake({}, 'property', 'className', directory);

Thoughts?

[joliss]

I don't really want to maintain this package anymore. I don't think ending up with tmp directories in CWD or other random places is a terribly great pattern, so it would probably be better to write something more sensible, either from scratch or based on this package. In any case, I don't want to be the one maintaining it. :-)